/Engine/Source/Editor/UnrealEd/Public/PackageTools.h
Converts a long package name to a file name. This can be called on package paths as well, provide no extension in that case. Will return an empty string if it fails.
Package filename, or empty if it failed.
static [FString](API\Runtime\Core\Containers\FString) PackageNameToFilename ( const [FString](API\Runtime\Core\Containers\FString) & PackageName, const [FString](API\Runtime\Core\Containers\FString) & Extension )